In a laboratory experiment, rashida observed water as it vaporized, froze, melted, and condensed. which of the following is a valid conclusion? a. she observed different changes of state. b. all of the changes required energy to be absorbed. c. each of these processes happens when the temperature is decreased. d. all of the changes required energy to be released.

(A) is the answer cause heating require to gain energy  and freezing require  to loss energy

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i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.